1. Field of the Invention
The present invention relates to an improved annular liner for pneumatic tires and to the method for preparation of the liner. In particular, the present invention relates to a tire liner which has an annular section of high temperature and pressure vulcanized and molded rubber, preferably prepared from a precured process retreading strip, adapted to be positioned opposite the tread and around the circumference of the inside of the casing of a tire.
2. Prior Art
Tire liners which fit inside a pneumatic tire casing adjacent to the tread area to provide puncture protection are well known to those skilled in the art. In general the tire liners are: (1) of the self-healing type which includes a material which flows into and/or cures in a puncture in a tire tread or other part of the casing and/or (2) the type that relies upon the thickness of the liner so that the object does not penetrate to the inside of the casing thereby allowing air to escape. The present invention is concerned with the type of liner which relies upon its thickness, although the self-healing components could be used with the tire liner of the present invention.
There are a number of patents showing the two types of the liners including U.S. Pat. Nos. 1,237,698; 1,390,249; 1,399,575; 1,462,117; 1,513,900; 1,683,454; 1,988,352; 2,550,773; 2,563,787; 2,802,505; 3,563,294; 3,993,114; 4,109,695 and 4,140,167 as well as Canadian Pat. No. 709,658; Belgian Pat. No. 510,001 and British Pat. No. 708,206.
One commercially available tire liner uses a foamed, flexible and elastic polymer, such as polyurethane, to form the liner which is pre-cast in a mold to the proper shape and dimensions. This construction is similar to the liner described in Canadian Pat. No. 709,658. The problem is that the foamed liner does not provide any significant resistance to penetration by a foreign object and the liner relies only upon its thickness, rather than any inherent toughness, to prevent foreign objects from penetrating to the inside of the casing. Also such liners cause the tires to overheat and they break down under high speed operating conditions. Also the liner is not to be used with radial type tires. When the tire goes flat, the tire liner is severely damaged or destroyed.